A wide variety of surgical applications require the placement of surgical screws in bone tissue. Some procedures use bone tissue as an attachment point for other devices such as titanium mesh, orthodontic anchors, resorbable or nonresorbable membranes. Other procedures require attachment of bone graft to host bone, such as the fixation of a bone block or graft or stabilization of a fracture. It is often necessary to stabilize soft tissues such as mucosa, skin, muscle or tendon, in which case bone provides a stable anchorage onto which soft tissues can be attached. Creating a stable and secure attachment point is difficult because the bone tissue must support large mechanical forces and the attachment of synthetic or graft structures to bone places enormous stress on both the bone and the attachment device at the point of attachment or fixation.
Traditionally, surgical screws have been used to attach a desired structure to bone. The desired attachment structure may be another piece of bone, a graft or synthetic prosthetic, a mesh or biocompatible implant, or a dental prosthetic. Ordinary surgical screws are attached to bone in the same manner that ordinary hardware screws employ. Using a driver, such as a screwdriver, the user contacts the head of the screw with an engaging fixture at the distal end of the driver and manually rotates the threaded portion of the screw until the screw penetrates the target site at a selected point and the attachment by the screw secures the selected attachment structure at the desired attachment point. The problem with current surgical screws is that the graphs or devices, which are typically being anchored to bone at the target site, interfere with visualization of underlying bone at the target site and can interfere with the proper placement of the screw into bone. Also, many surgical procedures, and particularly dental procedures, require precise placement of bone in confined spaces with delicate bone and tissue structures and difficult geometrics.
Moreover, anytime screws are used in surgical applications, it is particularly important that the screws be placed securely and stably and that any attached structure is precisely placed and completely secured to the bone at the target site and without damaging the bone that provides support for the attached structure. The task is particularly challenging with the limited fields of view inherent in dental applications, such as when placing an anchor, where visualization of the attachment of the fixture takes place between teeth and requires careful and stable securing of the structure to the jaw bone.
Thus, the existing surgical practices and apparatus have at least the following drawbacks: 1) the attachment structure must be held in place while the threaded portion of the screw is drilled into the bone under limited visibility; 2) the placement can be inaccurate and often damage the bone when the underlying bone is visually blocked by the screw, the attachment structure, or both; 3) driving a screw through surrounding membranes can cause the membrane to rotate and the attachment between the driver and the screw is generally unstable.
Accordingly, a need exists for an improved bone screw design that enhances a surgeon's ability to more carefully control the process of driving a screw into bone and improve the application of the attachment structure to bone while enhancing the surgeons' visualization of the procedure.